Stock Based Compensation and Stock Options (Details 4) (USD $)	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Options outstanding
Options outstanding, beginning, Shares	1,100,952	1,502,046
Options outstanding, beginning, Average price per share	$ 18.65	$ 17.10
Granted, Number of Options	191,900	22,300
Granted, Weighted Average Exercise Per Share	$ 23.46	$ 20.54
Options exercised, Shares	(64,976)	(131,146)
Exercised, Weighted Average Exercise Per Share	$ 13.40	$ 12.73
Cancelled - forfeited, Number of Options	(26,815)
Cancelled - forfeited, Weighted Average Exercise Per Share	$ 23.55
Cancelled- expired, Number of Options	(1,431)
Cancelled - expired, Weighted Average Exercise Per Share	$ 19.76
Options outstanding, ending, Shares	1,199,630	1,303,806
Options outstanding, ending, Average price per share	$ 19.60	$ 17.30
Ending outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 7 months 17 days
Ending outstanding, Aggregate Intrinsic Value	$ 11,602,070
Ending vested and expected to vest, Number of Options	1,048,483
Ending vested and expected to vest, Weighted Average Exercise Per Share	$ 18.99
Ending vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	3 years 5 months 27 days
Ending vested and expected to vest, Aggregate Intrinsic Value	10,775,566
Ending exercisable, Number of Options	516,511
Ending exercisable, Weighted Average Exercise Per Share	$ 15.14
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 6 months 26 days
Ending exercisable, Aggregate Intrinsic Value	$ 7,298,354